source:
asp3_tinet_ecnl_rx/trunk/musl-1.1.18/src/math/asinhf.c
Last change on this file was 337, checked in by , 6 years ago | |
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File size: 717 bytes |
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1 | #include "libm.h" |
2 | |
3 | /* asinh(x) = sign(x)*log(|x|+sqrt(x*x+1)) ~= x - x^3/6 + o(x^5) */ |
4 | float asinhf(float x) |
5 | { |
6 | union {float f; uint32_t i;} u = {.f = x}; |
7 | uint32_t i = u.i & 0x7fffffff; |
8 | unsigned s = u.i >> 31; |
9 | |
10 | /* |x| */ |
11 | u.i = i; |
12 | x = u.f; |
13 | |
14 | if (i >= 0x3f800000 + (12<<23)) { |
15 | /* |x| >= 0x1p12 or inf or nan */ |
16 | x = logf(x) + 0.693147180559945309417232121458176568f; |
17 | } else if (i >= 0x3f800000 + (1<<23)) { |
18 | /* |x| >= 2 */ |
19 | x = logf(2*x + 1/(sqrtf(x*x+1)+x)); |
20 | } else if (i >= 0x3f800000 - (12<<23)) { |
21 | /* |x| >= 0x1p-12, up to 1.6ulp error in [0.125,0.5] */ |
22 | x = log1pf(x + x*x/(sqrtf(x*x+1)+1)); |
23 | } else { |
24 | /* |x| < 0x1p-12, raise inexact if x!=0 */ |
25 | FORCE_EVAL(x + 0x1p120f); |
26 | } |
27 | return s ? -x : x; |
28 | } |
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